Today there are numeral methods for supporting an excavation. Using of helical multiple anchors as excavation support has speared recently. Because of wide range of applications of helical anchors, a massive number of experimental, numerical, and field studies have been carried out. This study works on the pullout capacity of helical multiple anchors by using FLAC 3D software. First, a verification test is carried out in order to confirm the method of simulation. Then, with the help of an extensive parametric study, the effect of different parameters on pullout capacity is observed. This study indicates that sharp growth in loading capacity is observed due to an increase in density of soil and diameter of helical plates. In addition, the results show that changes in the cohesion of soil have a few effects on the loading capacity of helical anchors. Moreover, the share of loading on the plates keeps remain if the space between plates is five times of helical plate diameter and more. In this situation, the failure mechanism is individual plate. Nevertheless, if the space between plates is less than five times of helical plate diameter, the share of loading on the first helical plate (near to excavation) goes up, but the share of loading on the rest helical plates drops dramatically. In this situation, cylindrical shear is the main failure mechanism. Therefore, the current study results demonstrate that the critical space between helical plates is five times of helical plates diameter.

In today’s world, roads are considered the main arteries of the global community. One of the most typical methods to build these routes is stabilizing the excavations on two sides of the roads. Using multiple helical anchors in excavation stabilization is one of the means recently used by many road and geotechnical engineers. The increasing use of multiple helical anchors has led to several laboratories, numerical, and field studies. Therefore, this study employed the FLAC 3D software also a three-dimensional numerical investigation of bearing capacity under different inclination angles in sandy soil. In the present study, the effect of soil installation, which is caused by installing helical anchors in the soil, has been studied on the load-bearing capacity of these helical anchors. For this purpose, first, a verification test is done to validate the modeling approach. Then, by performing a parametric analysis, the effect of different inclination angles, as well as the installation effect on the bearing capacity of the multiple helical anchors, are studied. The present study results show that the maximum bearing capacity of the helical anchors is achieved by the angle of 5 and 10 degrees. In addition, by investigating the installation effect, the bearing capacity of the helical anchors has been significantly reduced with respect to the number of helical plates and the density of soil.

Helical anchors with unique characteristics have several applications in constructing and reforming the foundations, as well as soil improvement. However, a limited number of study has been done on the use of helical anchors in walls and slopes stability. In the performed studies, the behavior of the helical anchor’s wall was investigated. For this purpose, a laboratory study was designed to evaluate the wall stability with three types of helical anchors and two types of back-slopes in sandy soil. The aim of the study was to investigate the effect of anchor’s shape and the back slope above the wall on the wall crest displacement. To increase the accuracy of measurements and determine the shear strains, photogrammetry and particle image velocimetry (PIV) methods were employed. Finally, to evaluate its implementation potential, the results were compared with those of the nailing method. The results of modeling revealed that an increase in diameter and the number of the helices led to decreasing in wall crest displacement. The reduction percentages were 30% and 60% respectively for increased diameter and increased number of helices and diameter. If the significant reduction in displacement is required, it is suggested to increase the number of helices without any changes in their diameter. Besides, anchors need a small amount of displacement to be activated and this issue cannot be solved by changing the type of helical anchor. Finally, the results indicated that the slip surface created on the wall of helical anchor using light surcharge is parabolic in shape.

Nowadays, helical anchors are one of the fastest methods of supporting excavations. The use of helical anchors is increasing, and recently they received more attention in researches. One of the most important factors for the design of helical anchors is their tensile capacity, to which less attention was paid in the literature compared with the helical piles. The present study uses a three-dimensional numerical modeling approach to investigate the tensile capacity of helical multi-plate anchors. For this purpose, first, the adopted numerical modeling methodology is verified. Then, a comprehensive parametric study is performed to investigate the effects of various parameters involving the soil type, soil cohesion, plate diameter, plate spacing, surcharge, and anchor inclination. The present study results show that the tensile capacities of the helical multi-plate anchors increase by increasing the plate’s diameter, surcharge, and soil relative density. However, the soil cohesion and anchor inclination have negligible effects. Moreover, the results indicate that the load-bearing shares of the shaft increase by increasing the surcharge and decreasing the plate diameter. In addition, the results show that the load-bearing shares of the plates stay about constant for S/D≥4 (S and D represent the plate's Spacing and Diameter, respectively). So that the failure mechanism of multi-plate anchors could be considered as the individual plate for S/D≥4 and cylindrical shear for S/D<4. In other words, the critical S/D ratio is 4. The union of failure zones formed around the plates in displacement contours for S/D<4 confirms this result.

The increasing rate of construction activities in urban areas is accompanied by excavation in the vicinity of existing structures and urban utilities. This issue has highlighted the importance of constructing protecting structures in order to control displacements and prevent damage to structures and their neighboring area. Among the important widely used wall stabilization techniques, one can name nailing and grouted anchors. However, these methods suffer some drawbacks such as annoying noise and vibration during the drilling, implementation difficulties below the water table, grouting problem, installation of strands and bars in the borehole in porous and collapse soils, and long curing time for the grout of post-tension anchors. Since the helical anchor method lacks many of the mentioned problems, it is now widely used in many applications.In the present work, a laboratory model of helical anchor stabilized wall is presented and evaluated. For this purpose, four types of anchors at 20° back slope are designed in a sandy soil and the effect of helix configuration (in term of its diameter and number of blades) is investigated. Considering the laboratory scale of the designed model, the results obtained using helical anchor were compared with numerical results of soil nailing wall by applying the particle image velocimetry (PIV) analyses.

The test box designed in this work is made of a metal plate with a thickness, length, width, and depth of 1.5 mm, 100 cm, 60 cm, and 30 cm, respectively, and a Plexiglas in its opposing side with a thickness of 50 mm. The soil used in the experiments was the dry sand of Soufian region in east Azerbaijan province of Iran. The soil is classified as SP according to USCS classification. The helical anchors were fabricated by welding the helical pitches to a metal shaft. The end part of the shafts is screw threaded such that to fasten a bolt to them. To start the experiment, the empty box was completely cleaned using the detergents to remove any pollution or soil on the Plexiglas and metal surface. Afterward, the sandy soil was poured on the wall floor and the facing was placed inside the box vertically. Again, the sandy soil was poured from both sides of the facing up to the installation height of the helices. Helices were installed in the assigned holes and their angle was adjusted through the pre-fabricated stencils. The soil height was increased up to the next row assigned for helices installation. These steps were repeated until reach the wall crest. After preparation of the physical model, its behavior during the preparation must be modeled. We first filled both sides of the model and then modeled the stability behavior of the helical anchor wall through excavating its facing opposed side. Overall, the wall was built through eight excavation steps.

The maximum displacement is related to the anchor type 1, which does not have enough bearing capacity under surcharge conditions. By changing the anchor type and increasing the number of helices, shear strains and their expansion in the wall back decline. The decrease in displacement rate by changing the anchor from type 1 to type 2 is 18%, which is due to the low bearing capacity of type 2 anchor compared to the type 1 anchor. Increasing the number of pitches from one to two (changing the type 1 anchor to type 3 anchor) showed a considerable decrease (i.e., 43%) in displacement rate. Increasing the number of pitches from 1 to 3 (changing the anchor from type 1 to type 3) resulted in a 62% decrease in wall crest displacement. This displacement decrease rate seems to decline with an increase in the number of helixes.The displacement rate for all four anchors is almost similar in two excavation steps, which probably is because of the need for displacement for activation of the anchors. One strategy to deal this issue in the sensitive projects and control the displacement is to apply post-tension helical anchors. Then, in stages 4 to 6, the displacement was almost constant due to four main reasons including wall rigidity, the presence of reinforcements, formation of pre-step displacement-induced tension force, and enough capacity of anchors to face with more displacement. In stages 6 to 8, type 1 and 2 anchors showed growing displacements due to the reduction and ending the wall rigidity and lower bearing capacity. In type 3 and 4 anchors, the maximum displacement was related to 4 initial stages. In type 1 and 2 anchors, which have two helical plates, almost a similar behavior was observed until stage 6 of excavation, but eventually type 3 anchors showed better performance because of higher bearing capacity to overall displacement.

In the present study, a physical model was designed to investigate the effect of helical anchors’ geometry on displacement rate of helical anchor wall and compare it with a nail wall. Overall, comparing the results obtained by conducting these experiments on a helical anchor stabilized wall and a nail wall revealed that:- Wall crest displacement is affected by the diameter and number of helices and decreases by an increase in bearing capacity. The increase in the number of pitches from one to two (single-pitch to double-pitch anchor) has a higher effect on displacement control compared to the case of changing the double-pitch to triple-pitch anchor. So, it can be stated that a further increase in the number of anchor pitches results in a declined performance of the anchors. All anchors need a slight displacement for activation. This issue cannot be resolved by changing the type of helical anchors. Hence, when the displacement required for activation of the anchors exceeds the allowable wall crest displacement, use of post-tensioned helical anchors is recommended.A comparison between nailing and helical anchor results revealed that the relative density of the wall stabilized with the helical anchor is less than that of the nail wall; and wall crest displacement in the helical anchor wall was very lower than that of nail wall. Thus, the helical anchor wall stabilization is preferred when other economic and technical requirements are met.

Helical anchors have been used to carry tension loads in different applications including transmission tower foundation, pipeline anchors, foundation repair elements, and excavation bracing. There have been numerous changes in the shape and size of helical anchors and piles since their first usage. Several researchers have studied their failure mechanism to find their pullout capacity. In this paper, the uplift capacity of helical screw anchors has been investigated through laboratory testing. Half-cut double-helix anchors were tested in a sand tank by varying helix size, helix spacing, and relative density of sand. A series of images were captured during the process of anchor pullout. The images were used to obtain displacement and strain fields by Particle Image Velocimetry (PIV). Load–displacement curves have been presented and compared to the earlier works. Afterwards, pullout capacity factors were calculated from peak load values. PIV analysis results were used to study the effects of helix spacing, helix size, and relative density of sand on the displacement fields. The results showed that the effect of helix spacing and soil density in increasing pullout load is more than that of helix size. Moreover, failure surfaces were discussed through displacement and strain fields. The findings indicated that failure surface above the top helix of deeply embedded anchors is a truncated cone with the angle of approximately ϕ/3, with the vertical and the failure surface shape between the two helices dependent on helix spacing.

The use of piles, helical anchors and, in general, helical foundations has considerably increased in the last 30 years. The adoption of this technology in the international and domestic codes of each country, as well as in research and studies, and, finally, the publication of numerous books and papers in this area, and the existence of manufacturers’ products, committees, and contractors of this technology has contributed to its expansion and development. However, such methods have progressed at a very slow pace in many countries, especially in developing countries. This paper attempts to assess the global advancement of the helical foundations by reviewing 292 papers from 1990 to 2020 and comparing the related research findings. This will help clarify the issue and determine the scope of technological progress. On the other hand, collecting valuable papers in this area will make it easier for researchers to make further research. Subsequently, the characteristics of this technology are highlighted and the reasons for its lack of progress in the developing countries are addressed. For this purpose, a questionnaire is sent to researchers, developers, designers, and contractors of the geotechnical projects. The purpose of this questionnaire is to specify the type of existing projects, the soil type of project site, the degree of familiarity with the helical foundation technology, the reasons for not using this method and the solutions available to expand and develop this method. Finally, there are suggestions to develop this approach and the issues that need further research.

Retaining walls are geotechnical structures built to resist the driving and resistant lateral pressure. In terms of serviceability life, these walls are divided into two groups including short-term structures (temporary), such as urban excavation project, and long-term (permanent) structures, such as Mechanically Stabilized Earth Walls (MSE Walls). Retaining walls are implemented by two main methods including Top-down and Bottom-up. Among the reinforcements applied in the Bottom-up walls, one can name geocells, geogrids, metal strips, and plate anchors. On the other hand, the common reinforcements applied in the Top-down walls are grouted soil nails and anchors and helical (screw) soil nails and anchors.Plate anchors are burial mechanical reinforcements that have one or multiple bearing plates with a bar or cable to transfer the load to an area with stable soil. Among different types of plate anchor applied in onshore and offshore projects, one can name simple horizontal, inclined, and vertical plate anchors, deadman anchors, multi-plate anchors, cross-plate anchors, expanding pole key anchors, helical anchors, drag embedment anchors, vertically loaded anchors (VLAs), suction-embedded plate anchors (SEPLAs), dynamically-embedded plate anchors (DEPLAs) like Omni-max and torpedo anchors, and duckbill, manta ray and stingray anchors.The present research reports the results from physical modeling of plate anchor retaining walls under static loading. The evaluation parameters in this work include the geometry, dimension, and reinforcement configuration of plate anchors on wall stability. PIV technique was employed to observe critical slip surface. It is worth mentioning that PIV is an image processing technique firstly used in the field of fluid mechanics to observe the flow path of gas and fluid particles. This method was used in geotechnical modeling by White et al. (2003) and few reports are already available about its application to observe wedge failure of mechanically stabilized retaining walls.

To carry out tests at a laboratory scale, a dimensionality reduction ratio of 1/10 was applied. Thus, all dimensions of the designed retaining wall were divided by 10. As a result, a retaining wall with a height and length of 3000 mm was reduced to a wall with 300×300 mm2 dimensions. To build a retaining wall, a chamber was designed with a length, width, and depth of 1000 mm, 300 mm, and 600 mm, respectively.The soil used in all tests was the sandy soil supplied from Sufian (in Eastern Azerbaijan, Iran). According to the Unified Soil Classification System (USCS), the soil is classified as poorly graded sand with letter symbol ‘SP’.To create a perfect planar strain condition and prevent any friction between the footing and the lateral sides of the test box, the footing length was selected 1 mm smaller than the 300 mm width of the test chamber. Therefore, the length, width, and thickness of footing were selected as 299, 70, and 30 mm, respectively.The length and diameter of applied tie rods were respectively 300 mm and 4 mm, which are the smaller scales of 3000 mm length and 40 mm diameter tie rod. The two sides of the tie rods were threaded to plate anchors and wall facing. Four polished square and circular anchor plates with two different areas were used. The area of small and medium circulars are respectively equivalent to the area of small and medium square plates.Because no post-tensioning occurs in these plate anchors, the horizontal and vertical distances were both selected as 1500 mm. By applying a dimensionality reduction coefficient of 1/10, a 150 mm center-to-center distance was obtained for reinforcements in the wall. Accordingly, three applied reinforcement configurations including 5-anchor, diamond, and square configurations were used. To construct permanent retaining wall facing, prefabricated or precast concrete blocks with a thickness of 300 mm were used. Wood (2003) conducted a dimensional analysis and introduced four types of material with different thicknesses for a 300 mm concrete facing in laboratory modeling. Accordingly, a 0.9 mm thick aluminum plate was used in the experiments performed in the present work.

With an increase in dimensions of anchor plates, an increase in bearing capacity of footing and a decrease in horizontal displacement of the wall are noticed. By comparing the 24 mm footing settlement in three configurations, with changing dimension of the plates from C1 to C2 and S1 to S2 respectively, 63% increases are observed in bearing capacity of the wall.An increase in anchor plate dimensions results in a significant decrease in wall displacement. Therefore, changing the plates from C1 to C2, S1 to S2 leads to 24% and 28% declination in wall displacement.By changing reinforcement configuration from square to diamond, diamond to 5-anchore, and square to 5-anchor, respectively, 27%, 31%, and 67.5% increases in bearing capacity for small plates, 9.2%, 27%, and 38% for medium plates are achieved using a comparison of the final loading steps in experiments. An analogy of percentages shows that a decrease in the effect of changing the reinforcement configurations on the bearing capacity of the wall with an increase in plate anchors dimensions is reached. 

In the present research, a set of laboratory experiments were carried out to evaluate the stability of mechanical retaining walls reinforced with plate anchors with different geometries (square and circular), sizes (small and medium), and configurations (diamond, square, and 5-anchor). The main results of the present work can be outlined as follows:• The maximum bearing capacity is for the 5-anchor configuration since it has one more reinforcement. After 5-anchor configuration, the diamond configuration results in a higher bearing capacity compared to the square configuration.• Circular anchor plates compared to square anchor plates provide a higher wall stability and in the most of the experiments lead to higher bearing and lower displacement in the wall.• Wall displacement in a diamond configuration with one less reinforcement shows a little difference with 5-anchor configuration. The maximum wall displacement occurs in a square configuration and more wall swelling is observed in the wall middle height due to inefficient anchors configuration in the wall.

Helical tubes have a tightly wrapped construction that is very efficient and provides excellent stability for managing two-phase flows. They also exhibit good thermal performance. With the increasing use of two-phase flows in helical tubes across many applications, it is crucial to further investigate the thermal and entropic characteristics of these flows in those helical tubes. This work aims to explore the hydrodynamic characteristics of helical tubes experimentally. The study tested different coil tube sizes by passing a two-phase air/water flow through them. To achieve this goal, a vertical helical tube with varying coil sizes is used. Water and air are specifically guided into the helical pipe, with the water and air mixture flowing downward and upward after being thoroughly mixed in a mixing chamber. The primary variable assessed is the pressure decrease. The collected experimental findings are evaluated to develop a correlation for pressure loss, with multiple linear regression being the primary focus of this work. The results indicate that decreasing the coil diameter results in reduced pressure drop in downward flow and increased pressure drop in upward flow. The maximum pressure drop ratio is around 1.25 in a downward flow and 1.63 in an upward flow. The highest pressure drop value is about 352 mbar for the coil of 100 mm diameter in downward flow and 541 mbar for the coil of 180 mm diameter in upward flow.

Career Orientations or career choices, can be affected by internal and external factors. External factors are the environmental conditions the reward and the final achievements of selecting a career choice are dependent on. Internal factors refer to the needs, beliefs and competencies of an individual that can be related to his/her job. The result of exploratory factor analysis of Schein's career anchor inventory supported the 8 factor structure of career anchors with one change. Then, the internal antecedents of managerial and technical orientations of 200 Iranian programmers were identified using multiple regression analysis. In addition, perception of people about the compensation system as an external factor has been found to affect the above relationships, as a moderating factor. The results revealed significant relationships between technical anchor and technical orientation, challenge, general management, entrepreneurship and job security anchors and managerial orientation.